During large magnetic storms, wind disturbances produced by auroral phenomena can affect the whole thermospheric circulation and associated ionospheric dynamo currents for many hours after the end of the storm. This paper presents a morphological analysis of the ground magnetic field disturbance related to the storm winds observed on March 23, 1979, the day after the Coordinated Data Analysis Workshop (CDAW) 6 events. The distrubance in the magnetic field variations is observed on a planetary scale, and its pattern does not correspond to that of the regular field variations related to the undisturbed atmospheric dynamo. ¿ American Geophysical Union 1990